There are a number of U.S. patents that disclose electronic apparatus for printing indicia on labels, some of these are restricted to hand held units and others that disclose tabletop units. Hand held labeling machines are disclosed, for example, in U.S. Pat. No. 4,264,396, Stewart; U.S. Pat. No. 4,407,692, Torbeck; U.S. Pat. No. 4,473,426, Goodwin et al.; U.S. Pat. No. 4,477,305, Hamisch; U.S. Pat. No. 4,490,206, Makely; U.S. Pat. No. 4,497,683, Hamisch; U.S. Pat. No. 4,498,947, Hamisch et al.; U.S. Pat. No. 4,511,422, Hamisch et al.; U.S. Pat. No. 4,544,434, Mistyurik; U.S. Pat. No. 4,556,442, Torbeck; U.S. Pat. No. 4,561,048, Hamisch et al.; and U.S. Pat. No. 4,680,078, Vanderpool et al. Tabletop units for this general purpose, some of which are portable are described in U.S. Pat. No. 4,440,248, Teraoka; U.S. Pat. No. 4,501,224, Shibayama; U.S. Pat. No. 4,630,538, Cushing; and U.S. Pat. No. 4,655,129, Wirth et al.
The electronic machines for printing labels of the type disclosed above all include the same general combination of elements, a print head, means for feeding labeling media to be printed past the print head, a microprocessor, a read only memory programmed with appropriate instructions to operate the microprocessor, a random access memory, a keyboard with letter, number, and function keys for the entry of alphanumeric information and instructions concerning the indicia to be printed, and a visual display such as a LED, LCD unit to assist the operator in using the machine. In a hand held printer, these components may all be enclosed in a single housing.
The labeling media comprises a series of labels that are attached to a carrier strip. The carrier strip is fed through the printer and legends are printed on the labels. The labels are then removed from the carrier and attached to the objects needing identification. As there are many types of label applications, there are many combinations of labels and carrier strips that provide labels of varying sizes, colors and formats.
A particular type of print head employs thermal transfer printing technology. Thermal transfer printing uses a heat generating print head to transfer a pigment, such as wax, carbon black, or the like, from a thermal transfer ribbon to a labeling media. By using digital technology, characters are formed by energizing a sequence of pixels on the print head which in turn melt the wax or other pigment on the ribbon transferring the image to the labeling media.
In a known thermal transfer printer such as a label printer, labeling media is fed by a paper feed roller simultaneously with a platen roller feeding an ink transfer ribbon. While the labeling media driven by the feed roller runs between the print head and the rotating platen roller, the transfer ribbon is passed between the print head and the platen roller by rotating the platen roller. As a result, the labeling media and the transfer ribbon pass together in overlay relationship between the print head and the platen roller.
Many of prior art thermal printers disclosed above waste portions of the transfer ribbon, labeling media or both. Since the labeling media and the transfer ribbon are fed together at once, if information is printed on a part of a label, or if the labeling media has a non-printing section, that portion of the transfer ribbon which corresponds to the non-printed section is wastefully advanced. One method of reducing this waste is to reverse direction of the ribbon to use the previously wasted portion.
A more significant problem is wastefully transferring labeling media. After printing, labeling media advances to a "cut" or "dispense" position, which requires advancing the labeling media past a label that could otherwise have been printed. One method of reducing this waste is to reverse direction of the ribbon and labeling media to use the previously wasted portion. However, reversing the ribbon can introduce ribbon wrinkling which leads to misprinted labels.